Musical inspirations behind Doom's music

Much of Doom's soundtrack is inspired by early '90s heavy metal music, and fans have long noted similarities between tracks from Doom's soundtrack and popular heavy metal songs. A well-known page on Doomworld titled Bobby Prince is a Filthy Thief details some of the more obvious similarities.

It is known that in developing Doom's music, Bobby Prince had a small collection of heavy metal CDs given to him by John Romero that were being used as inspiration for covers. In 2007, some of Doom's unused music tracks were released by John Romero, and metadata comments in these files name the tracks that inspired them. Using available data it is possible to build up a map of what was likely to have been in the collection used by Prince.

Definites
The following albums were definitely used as inspiration for Doom's music; this is substantiated by evidence from the metadata comments in the unused music tracks and in the MIDI format version of the songs found in os2.wad:

Alice in Chains - Dirt
 * Released September 1992. Referenced in metadata in seven different MIDI files.
 * Most tracks weren't used but "Them Bones" was used for "Bye-Bye American Pie", heard in Barrels o' Fun.
 * "Angry Chair" was also used for "Adrian's Asleep" in Bloodfalls.

Alice in Chains - Facelift
 * Released August 1990. Referenced in metadata in two MIDI files.
 * "We Die Young" was used for "Hiding the Secrets", as evidenced by M_E1M9's metadata.

Metallica - Master of Puppets
 * Released March 1986. Referenced in metadata.
 * The namesake song of the album, Master of Puppets, was used for At Doom's Gate, as evidenced by M_E1M1.

Metallica - Ride the Lightning
 * Released July 1984.
 * "Fight Fire With Fire" is cited in M_E2M3's metadata.

Pantera - Vulgar Display of Power
 * Released February 1992. Referenced in metadata.
 * "Rise" inspired "Kitchen Ace (and Taking Names)", heard in Command Control, confirmed by M_E1M4's metadata.
 * "Mouth for War" inspired the untitled song used in Fortress of Mystery and  Hell Keep.
 * "This Love" inspired "Waiting for Romero to Play", heard in The Courtyard /  Monster Condo.
 * "Walk" inspired un51.mid from the unused music collection.

Slayer - South Of Heaven
 * Released July 1988. Referenced in metadata in two MIDI file (un48.mid), though another file is also a cover of a track from this album (un52.mid).
 * "Behind The Crooked Cross" was used for "Deep Into The Code", heard in Pandemonium.
 * "South of Heaven" was used for "Shawn's Got The Shotgun" heard in Dead Simple,  The Citadel, and  The Living End.
 * "Silent Scream" is referenced in the metadata for M_E2M1, though this file also references AC/DC's "Big Gun" which is a better fit.

Soundgarden - Badmotorfinger
 * Released October 1991. Metadata in four MIDI files reference two songs from this album, the first two tracks from the album. However, only two of the MIDI files coincide with the tracks.
 * "Rusty Cage" was used for un31 from the unused music collection.
 * "Outshined" was used for un32 from the unused music collection.

Stone Temple Pilots - Core
 * Released September 1992. Metadata in two MIDI files reference tracks from this album (the first two tracks).
 * "Sex Type Thing" inspired "Into Sandy's City", heard in The Pit.

AC/DC - Big Gun (single) or Last Action Hero soundtrack
 * "Big Gun" is referenced in the metadata in two MIDI file (un44.mid and M_E2M1); the single was released June 1993.
 * The song was used as inspiration for "I Sawed The Demons", heard in Deimos Anomaly.
 * Romero might have had the single, but it's equally plausible that he had the Last Action Hero soundtrack, which consisted primarily of songs by heavy metal bands that would have fit with the rest of the collection here.

Speculative
The following albums are not referenced in metadata comments. However, in each case, there are strong similarities to Doom's music tracks.

S.O.D. - Speak English or Die
 * Not referenced in metadata, but several of the unused MIDI tracks bear a strong resemblance to tracks off this album: specifically the songs "Pi Alpha Nu", "Milano Mosh" and "Speak English or Die"
 * The track "Sargent D & the S.O.D." was likely used as inspiration for "Facing the Spider" used in Dis.

Body Count - Body Count
 * Released March 1992. Not referenced in metadata.
 * "Body Count's in the House" inspired "Donna to the Rescue", heard in Slough of Despair and Perfect Hatred, despite what the metadata references as "Outshined" by Soundgarden.

Soundgarden - Badmotorfinger
 * The track "Slaves & Bulldozers" inspired the unused track un36, despite what the metadata references as "Outshined" from the same album.

Black Sabbath - Dehumanizer
 * Released June 1992. Not referenced in metadata.
 * "After all (the dead)" inspired "The Demon's Dead" used in Refueling Base and  Suburbs.

Mislabels
The following track is mistakenly referenced in the metadata.

Soundgarden - Badmotorfinger
 * "Outshined" is referenced in the metadata of un32, un36 and un37 from the unused music collection, yet is only correct for un32.